The invention relates to a device for fixing a fan-blade assembly onto a shaft suitable for being driven in rotation by a motor.
A fixing device of this type finds a particular application to the equipment of motor vehicles, and especially to the fixing of a blade assembly of a motor-driven fan unit.
Such a unit makes it possible to accelerate the speed of an airflow which, for example, passes through the radiator serving for cooling a motor-vehicle engine.
Such a fan assembly, also called turbine, usually comprises a hub, also called xe2x80x9cbowlxe2x80x9d, from which arise a plurality of blades which extend radially outwards. These blades have outer extremities which are either free, or preferably joined together by a profiled ring, also called xe2x80x9cshroudxe2x80x9d.
Such a fan assembly is generally produced by moulding from plastic, for example from loaded polyamide, and it is fixed onto the motor shaft by fixing means of the nut-and-bolt type with the interposition of an elastic coupling produced in the form of a ring made of elastomer material or the like.
These known fixing means, however, have the drawback of not sufficiently reducing the parasitic imbalance phenomena which arise when the centre of gravity of the fan assembly is not on the rotational axis of the motor shaft.
These imbalance phenomena stem essentially from the rigidity and from the geometry of the link between the blade assembly and the motor shaft.
In particular, it has been observed that the ring made of elastomer material has a tendency to age over time and to lose its elastic properties.
This results in high levels of imbalance which generate vibration at given rotational frequencies, as well as giving rise to a reduction in the reliability of the moving parts.
Furthermore, these known fixing devices have the drawback of requiring tooling for fixing the blade assembly, which complicates assembly and manufacturing.
The object of the invention is especially to surmount the abovementioned drawbacks.
The invention aims, in particular, to obtain a device for fixing a blade assembly onto a motor shaft which makes it possible to eliminate vibration of the blade assembly by reducing the levels of imbalance.
The invention also aims to obtain a fixing device of this type which retains its properties over time.
It also aims to obtain such a fixing device which enables effective and rapid fixing of the blade assembly onto the motor shaft, without requiring special tooling.
To that end, the invention proposes a device for fixing a fan-blade assembly onto a motor shaft, which comprises a drive hub integral with the shaft and suitable for serving as a support for a hub of the blade assembly, as well as a stop ring slipped on around the shaft and equipped with elastic recall means, so as to press the hub of the fan assembly elastically against the drive hub.
It results therefrom that the blade assembly is assembled and held axially by a stop ring endowed with elastic properties, and by way of a drive hub which is integral with the shaft of the motor.
While the blade assembly is rotating, and under the dynamic effects transmitted to the structure of the blade assembly, the stop ring, because of its elastic properties, deforms and takes up the forces, which makes it possible to realign the main inertial axis of the blade assembly onto the main inertial axis of the motor shaft.
According to another characteristic of the invention, the drive hub is fixed rigidly onto the shaft.
Advantageously, the drive hub is suitable for being inserted at least partly into the hub of the blade assembly so as to make them integral in rotation via a shape-interlocking link.
In one advantageous embodiment of the invention, the drive hub comprises sectors which are offset at angles and suitable for being inserted into matching-shaped recesses which the hub of the blade assembly includes.
According to another characteristic of the invention, the elastic means for recall of the stop ring are suitable for being engaged in a groove of the shaft.
These elastic recall means advantageously comprise elastic tongues extending radially within a central aperture of the stop ring.
These elastic tongues are advantageously of generally biconical shape. In one preferred embodiment, these elastic tongues are spaced at angles and present in numbers of greater than five.
Advantageously, the stop ring is produced in a single piece from an elastically deformable material, in particular from spring steel.